paper tiger 纸老虎

buck the tiger 玩纸牌(特指与赌棍玩牌)

tiger sweat 威士忌酒

work like a tiger生龙活虎地工作

three cheers and a tiger三声欢呼一声吼

a narrow escape 虎口余生

a nation of invaders 虎狼之国

How can you catch tiger cubs without entering the tiger's lair?
不入虎穴, 焉得虎子?

have a tiger by the tail/ He who rides a tiger is afraid to dismount. 骑虎难下

to brag and bully by assuming other people’s authority 狐假虎威

a strategic fortress as if guarded by a tiger and a dragon 虎踞龙盘

to be passionate about something at the beginning but soon lose their interest 虎头蛇尾

Sitting on a hill watching tigers fight 坐山观虎斗 (It means someone takes a side in a fight until one party overwhelms their enemy. )

A goat in tiger's skin 羊质虎皮 (It means someone who appears strong on the outside but is timid on the inside.)

Three people make a tiger. 三人成虎(The idiom suggests that gossip can be as ferocious as a tiger.)

A new-born calf has no fear of the tiger. 初生牛犊不怕虎。

drive a tiger out from the front door while a wolf comes in the back 前门拒虎，后门进狼。

like a tiger with wings 如虎添翼(It means someone's might is doubled.)

to lure the tiger form the mountain 调虎离山